This invention relates to a sealing apparatus having a composite material consisting of a sealing lip formed of a resin material and a sealing portion formed of a rubber-like elastic material, and a method of manufacturing thereof.
A conventional sealing apparatus is manufactured by accumulating a number of parts, as shown in FIGS. 23, 24, followed by caulking.
The sealing apparatus 100 shown in FIG. 23 is assembled by continuously baking a rubber lip 102 and a peripheral gasket 103 direct to a peripheral side metal ring 101 followed by vulcanization forming, inserting a resin formed sealing member 104 and an assembly reinforcing metal ring 105, and mechanically caulking the end portion 101a on the sealed fluid side O of the peripheral side metal ring 101, opposite to the atmospheric side A. A sealing apparatus 200 is assembled, as shown in FIG. 24, by installing a sealing ring 202 onto the outside of a peripheral side metal ring 201, inserting a rubber lip 203, a resin sealing member 204, a flat washer-shaped metal ring 205, and a dust lip 206 to the inside thereof, and mechanically caulking the end portion 201a on the sealed fluid side O of the meal ring 201, opposite to the atmospheric side A. The sealing apparatus 100 significantly reduced the number of parts items, compared with the sealing apparatus 200, which has lead to the facilitation and reduction in cost of the manufacture.
However, some problems were encountered in assembling the sealing apparatuses of FIGS. 23 and 24, including the generation of powder or metal powder from a surface coat in addition to the complicated and expensive caulking process of the periphery in the aspect of process, and the rusting by breakage of the surface treatment coat, the reduction in sealing function by the adhesion of the above powder to a product, and the like in the aspect of quality of product. Further, the exposed peripheral metal surface often damaged the associated housing, affecting the sealing property.
Further another conventional sealing apparatus is shown in FIG. 25. This sealing apparatus 300 shown in FIG. 25, which seals the clearance between concentrically relatively moving housing 310 and shaft 311 separately to the atmospheric side O and the sealed side M, mainly comprises an L-shaped sectional metallic reinforcing ring 301 for holding the form of the sealing apparatus 300, a first sealing member 302 formed of a rubber-like elastic body which is vulcanization formed on the reinforcing ring 301, and a second sealing member 303 formed of a resin material which is fixed so as to be nipped by the reinforcing ring 301 and the first sealing member 302.
The reinforcing ring 301 has a fitting portion 301a for fixing the sealing apparatus 300 onto the inside surface of the housing 310 and a flange portion 301b extending radially inward from the fitting portion 301a, and the fitting portion 301a has a peripheral sealing portion 302a formed integrally with the first sealing member 302 on its outside surface.
The sealing portion of this sealing apparatus 300 is formed on two members compositely constituted, enabling the use under a severe condition where it is difficult to satisfy high sealing performance over a long period only with a lip formed of a general rubber-like elastic Body.
Namely, the sealing portion is provided with a first sealing lip 302b of the first sealing member 302 and a second sealing lip 303a of the second sealing member 303, and a different characteristics are imparted to the respective lips to make the sealing portion more functional.
In this conventional apparatus, a material having high wear resistance or heat insulating characteristic by PTFE (ethylene tetrafluoride), for example, is adapted as the resin material for the second sealing lip 303a, so that the second sealing lip 303a has a holding function for minimizing the wear or deformation even when energized to the sliding surface of a shaft 311 by a high pressure on the sealed side M in the operation of the sealing apparatus 300 (mainly the rotation of the shaft 311), and preventing the reversion or movement of the first sealing lip 302b, whereby the sealing performance can be held over a long period.
A thread groove 303b for generating a pumping effect is formed on the surface opposed to the sliding surface of the shaft 311 of the second sealing lip 303a, and it is worked so as to return to the sealed side M the sealed fluid which is apt to flow out from the sliding surface of the shaft 311 onto the atmospheric side A during the rotation of the shaft 311, thereby holding high sealing performance.
On the other hand, for the first sealing lip 302b of a rubber-like elastic body, the sealing of the sealed fluid in the stoppage of the shaft 311 is rather an important function in this prior art, although the sealing property by itself is necessary in the rotation of the shaft 311.
Thus, such a conventional apparatus is constituted so that the characteristics of two different materials can be brought out and skillfully utilized to attain high sealing property.
FIGS. 26a and 26b are views illustrating a method of manufacturing the sealing apparatus 300 shown in FIG. 25. For the detailed description, refer to Japanese Patent Application No. 2-27386 by the present applicant.
In FIG. 26a, a mold 400 mainly comprises a lower mold 401 and an upper mold 410. The lower mold 401 is divided into a first mold 402 defining the bottom surface, a second mold 403 defining the radially outer wall surface, and a core 404 defining the radially inner wall surface. The outside surface of he core 404 has a male screw portion 404a cut therein.
On the other hand, the lower surface of the upper mold 410 has an annular projecting portion 411 to be inserted into the lower mold 401. When the mold is clamped, an annular cavity 420 is formed between the projecting portion 411 and the lower mold 401.
The vulcanization forming of the sealing apparatus 300 is performed in the following manner.
A reinforcing ring 301, and a rubber material 302xe2x80x2 as the second sealing member 303 and the first sealing member 302 are arranged in the lower mold 401 in this order.
As the second sealing member 303, a resin material such as PTFE is preliminarily formed into an L-shaped section by cutting work. Although it can be also considered that the second sealing member 303 formed of a material having a flat washer shape or funnel-like washer shape, for example, is used instead of the cutting work into the L-shaped section, and formed into the L-shaped section by mold clamping, problems such as the slippage of the forming position, the insufficient pressurization of the thread groove 303b caused by the consumption of the pressure for forming it for the formation of the L-shaped section, and the like must be taken into consideration in this case, because the second sealing member 303 is energized to the reinforcing ring 301 and the male screw portion 404a of the core 404 through the rubber material 302xe2x80x2.
The mold is then clamped as shown in FIG. 26b followed by heating and pressurization. The rubber material 302xe2x80x2 is fluidized within the cavity 420, carried along the surfaces of the second sealing lip 303a of the second sealing member 303 and the reinforcing ring 301, and spread to the whole area within the cavity 420.
The second sealing lip 303a of the second sealing member 303 softened by heat is then pressed onto the surface of the male screw portion 404a by the pressure of the fluidized rubber material 302xe2x80x2 to form the thread groove 303b corresponding to the male screw portion 404a. 
After the completion of the vulcanization forming, the mold is opened to take out a molding, and the excessive portion of the first sealing member 302 is properly cut, thereby completing the sealing apparatus 300.
In such a conventional method, however, the sealing apparatus 300 having the composite sealing portion as described above requires a special consideration with respect to the bonding of each constituting element manufactured from different materials.
Namely, the second sealing member 303 formed of a resin material such as PTFE is generally poor in bonding property with other materials, and the bonding surface with a rubber-like elastic body, for example, is often relatively easily peeled by the addition of an external force although it seems to be closely adhered thereto by vulcanization forming, or when the sealing lip 303a of the second sealing member 303 is radially extended in order to insert a shaft thereto, the peeling is likely to progress also from the portion with the reinforcing ring 301 by the addition of a large stress to the second sealing member 303.
Thus, the second sealing member 303 is subjected to a surface treatment by applying an adhesive followed by baking, so that the bonding strength with the first sealing member 302 and the reinforcing ring 301 in vulcanization forming is increased to hold the sealing performance.
In the connection with the reinforcing ring 301 formed of a metallic material, a mechanical fitting means (for example, irregularities of the surface or a communicating hole) is provided on the flange portion 301b of the reinforcing ring 301 to improve the bonding strength, but this along makes the sealing performance limited.
The adhering process described above, which generally followed, as the bed treatment of PTFE, a chemical treatment for dipping the second sealing portion in a liquid compound such as metal sodium, and required facilities and materials for the treatment process and an extremely precise process control. This tended to reduce the working efficiency and increase the cost. Further, in recent years, the problem of environmental protection, such as disposal of waste solution, must be taken into consideration.
This invention has one object to provide a sealing apparatus and a method for manufacturing it in which a sealing portion using a resin material can be firmly fixed without losing the sealing property of the sealing portion, and chemical treatment and adhering process which were necessary in the past can be abolished.
This invention has another object to provide a sealing apparatus of high quality which can be easily manufactured at low cost, and a method of manufacturing it.
A sealing apparatus according to one mode of this invention comprises an annular sealing lip formed of a resin material, a reinforcing ring having a bent section for nipping the peripheral end portion of the annular sealing lip, and a sealing portion formed of a rubber-like elastic material and vulcanization formed integrally with the reinforcing ring and the annular sealing lip.
The annular sealing lip is thus nipped by the reinforcing ring regardless of its material, and laid into a firmly bonded state while holding the sealing property. The sealing property is improved by the sealing portion formed of the rubber-like elastic material.
The annular sealing lip is preferably provided with a thread groove. This leads to an increase in flexibility of the annular sealing lip and, hence, to an improvement in sealing property of the annular sealing lip in the operation of the sealing device and an improvement in working property in the assembling of a shaft or the like into the sealing apparatus.
The annular sealing lip is also preferably formed into a flat washer shape. This shape facilitates the manufacture of the annular sealing lip.
A method of manufacturing a sealing apparatus of this invention comprises the steps of preliminarily integrating a flat washer-shaped annular sealing lip formed of a resin material with a reinforcing ring having a bent section for nipping the peripheral end portion of the annular sealing lip as an assembled member, and installing this assembled member to a mold to subject a sealing portion formed of a rubber-like elastic material to the vulcanization forming.
The above mold is preferably provided with a thread groove forming portion for forming a thread groove on the annular sealing lip, so that the thread groove is simultaneously with the vulcanization forming of the sealing portion.
In another mode of this invention, the sealing apparatus comprises an integrally built-up assembly composed of a first metal ring having an axially extending peripheral portion and a flange portion extending radially inward from the end portion the sealed fluid side of the peripheral portion, a second ring having an axially extending peripheral portion and a flange portion extending radially inward from the end portion on the sealed fluid side of the peripheral portion, and a resin ring having a resin formed first sealing lip, the inside surface of the peripheral portion of the first metal ring being fitted to the outside surface of the peripheral portion of the second metal ring to nip the base end portion of the resin ring between the flange portion of the first metal ring and the flange portion of the second metal ring; and a rubber-like elastic body formed covering portion composed of at least a peripheral covering portion for covering the outside surface of the first metal ring, a sealed fluid side covering portion for covering the sealed fluid side end surface of the flange portion of the first metal ring, and a second sealing lip portion provided on the sealed fluid side of the first sealing lip portion, which are continuously formed, and the assembly is integrally held by the covering portion.
According to the constitution like this, the complex and expensive caulking process is dispensed with in the manufacturing process since the assembly is integrally held by the covering portion, enabling the simplification and reduction in cost of the manufacturing process. Since the generation of powder or metal powder from the metal surface treatment coat by the caulking process is thus eliminated, the quality is improved without losing the sealing property by the adhesion as foreign matter of the powder to the sealing apparatus. The quality is further improved since the problem of the rusting by breakage of the metal surface treatment coat in the caulking process never occurs.
Since the covering portion is continuously formed, the passage of airtight leak which is generated in building of the assembly is sealed by the covering portion, and the reliability is improved. Further, the continuous formation of the covering portion dispenses with the complete quality control for foreign matter, flaw, forming failure and assembling failure which might lose the airtightness with respect to each member of the assembly. Thus, the manufacturing process is simplified, enabling a reduction in cost.
Since the outside surface of the first metal ring is covered with the peripheral covering portion formed of a rubber-like elastic body, the sealing function on the peripheral side can be sufficiently ensured without the metal surface damaging the inside surface of the housing to affect the sealing property, and the functional reliability is improved.
In further another mode of this invention, the resin ring is assembled onto the anti-sealed fluid side of the flange portion of the first metal ring in the inner portion of the first metal ring, the second metal ring is press-fitted into the anti-sealed fluid side of the resin ring in the inner portion of the first metal ring to fit the inside surface of the peripheral portion of the first metal ring to the outside surface of the peripheral portion of the second metal ring, and the base end portion of the resin ring is nipped between the flange portion of the first metal ring and the flange portion of the second metal ring, thereby integrally building the assembly, and the covering portion is formed integrally with the assembly arranged within a mold by vulcanization forming.
According to the constitution like this, the complicated and expensive caulking process is dispensed with since the assembly is held by the covering portion formed integrally with the assembly, enabling the simplification and reduction in cost of the manufacturing process. Since the generation of powder or metal powder from the metal surface treatment coat by the caulking process is thus eliminated, the quality is improved without losing the sealing function by the adhesion as foreign matter of the powder to the sealing apparatus. The quality is further improved since the problem of the rusting by breakage of the metal surface treatment coat in the caulking process never occurs.
Since the rubber-like elastic body material is penetrated and filled into the clearance of each member of the assembly, in the process of vulcanization forming, to seal the clearance which forms the passage of airtight leak, the reliability is improved. Further, the continuous formation of the covering portion dispenses with the complete quality control for foreign matter, flaw, forming failure and assembling failure which might lose the airtightness with respect to each member. Thus, the manufacturing process is simplified, enabling a reduction in cost.